Lighting fixture



June 1o, 1941. A L L. STEWART 2,244,737

LIGHTING FIXTURE Filed Dec. 5l, 1937 5 Sheets-Sheet 1 June 10, 1941. L, STEWART y 2,244,731

LIGHTING FIXTURE Filed Dec. 3l. 1937 5 Sheets-Sheet 2 E11/anton' June l0, 1941. L. L STEWART 2,244,737

LIGHTING FIXTURE Filed Dec. 3l, 1937 5 Sheets-Sheet 3 .lum 1o, 1941. l L L. STEWART 2,244,737

LIGHTING FIXTURE Filed Dec. 3l, 1937 -5 Sheets-Sheet 4 Patented June 10, 1941 2,244,737 LIGHTING FIXTURE `Lemuel L. Stewart, Elkhart, Ind., assigner to The Adlake Company, a corporation of Illinois Application December 31,1937, Serial No. 182,859

(Cl.A 24o-7.35)

2 Claims.

Due to limitations in vavailable power, lightingfixtures used on railway cars, buses and the like, should provide sufficient illumination at the reading plane for easy reading, but no more general illumination than is required for practical purposes.y Highly efficient, specially designed lighting fixtures are necessary to meet specifications of this kind, and the principal .object 4of this invention is to provide such fixtures,

A further object of the invention is to introduce color into the light which is given off by the fixture without materially impairing the eiliciency of the fixture as a Whole.

Practicability of fabrication, ease of maintenance, and cheapness in cost are other desirable attributes of the fixtures shown in the accom,

of the preferred forms of the invention;

Fig. 3 is a bottom plan view of the fixture shown in Fig. 2;

Fig. 4 is a. fragmentary cross-sectional view showing fixtures built into the underside of the baggage racks;

Fig. 5 is a cross sectional view through the fixture shown in Fig. 4;

Fig.- 6 is a bottom plan view of the fixture cover shown in Fig. 5, a portion being cut away, as indicated by the section line 6 6 in Fig. 5;

Figs. 7 and 8 show modified forms;

Fig. 9 is a cross sectional view of a railway car which, for the purposes of illustration, is equipped on the left side with the fixture shown fixture shown inFigs. 1l and 13;

Figs. 10 and 11 are bottom plan views of the fixtures shown in Figs. l2 and 13, respectively; and

Figs. l2 and 13 are sectional views showing another type of fixture coming within the broad scope of this invention.

The choice of certain preferred and modified forms of the invention for illustration and description is for the purpose of complying with sec. 4888 of the Revised Statutes, but it should be understood that the claims should not be limited by these specific embodiments of the invention unless required by the prior art. g

In designing the electrical equipment for a railway car, the engineer in charge usually allows a given number of watts, say 1500 watts, for the car lighting equipment. Other electrical power demands' are similarly budgeted and then the size and electrical characteristics of the generator, relays and other electrical equipment are determined.

The recent trend toward light-weight cars necessitates cutting down on the weight of the electrical equipment carried by each car, with the result that every effort is being made at the present time to reduce the amount of power required for car lighting. To accomplish this end, highly efficient lighting fixtures must be used.

Broadly speaking, the problem can best be handled by using efficient spotlight units which give the required illumination at the reading plane, but no more general illumination than is necessary for lighting the aisles and giving a general pleasing effect to the car interior.

The fixtures shown in the drawings and hereafter described accomplish these objects and meet the other requirements of practical design by having a minimum number of parts, by being easy to maintain,l and by being capable of adjustments which enable the desired lighting characteristics to be readily obtained after the installation of the fixtures has been completed. v

Referring now to Figs. l-3 inclusive, lighting fixtures generally designated 2li, are shown mounted on the ceiling of the lower deck of a railway car 2|,-one fixture being mounted above each pair of seats 22. The fixtures are recessed into the lower deck ceiling, the finish sheet of which is indicated at 23 (Fig. 2) and each com-l prises a standard lamp 2l screwed into a socket '23 which is adjustably supported by a collar 26 which rests upon and is capable of lateral adjustment relative to a reflector generally designated 21.

The reflector is shown as a sheet metal stamping having a polished reflecting surface 23, but it may be of any approved design and preferably is provided with a screw thread 26 adjacent to its mouth to receive the threads 30 formed on the glass cover, which is generally designated 3l. The threads 29 of the reflector may terminate in a marginal finish fiange 32.

The-co1lar 26 is split, as indicated at 33, to provide a clamping jaw 34 which may be made to grip the socket n25 and hold it in any desired adjusted position along a vertical axis by the tightening of a screw 36. Lateral adjustment of the lamp within. the reflector 21 is accomplished by movement of the collar 26 on the top fiat surface 36 ofthe reflector, the desired adjusted position being held by a small screw 31 which travels in a slot 36 provided in the colla-r 26.

The xture is preerably ventilated by provid: ing openings 39 and 48 in the reflector, or it may be made of a suitable heat dissipating material such as aluminum.

The fixture cover 3l is made of glass or other suitable transparent material as for example certain plastic material of which Phenol-formaldehyde compounds, Urea-formaldehyde compound, Methyl-methacrylate resin, Cellulose acetate are the most suitable. The cover comprises a lens portion di and light diffusing portion di, the former having its radius of curvature chosen to give the desired distribution of concentrated light on the reading plane immediately beneath the fixture. The light diiiusing portion B2 of the cover preferably has a plurality of annular prisms or ribs d3 which are shaped to provide evenly distributed illumination or any other desired distribution of light. 4

The cover 3l is readily secured to the ixture by screwing it into the reflector 2l, the upper margin oi the cover being serrated as indicated at it to cooperate with a spring pawl d which locks the coveiin place and prevents it from accidentally being unscrewed by jarring oil the car.

It will be observed that the light from the lamp 24 is concentrated by the reflector 2l on the lens portion il of the cover and the lens serves to collect the light rays and transmit them in the form ci a beam on the reading plane below. A certain amount of light, however., will pass out laterally through the diusing portion li2-of the cover and the prisms i3 will serve to distribute these rays according to general illumination requirements. The prisms bend the light rays from the source laterally and upwardly to provide general illumination for the upper portion of the car without glare to the passengers below. v

It is possible to give the vertical beam emanating from the xture a quality o color (the lamp 2li being a source of white light) by placing a color screen d6 along the inner wall o the light diffusing portion 2 of the cover. The screen may constitute a relatively thin sheet of gelatin or other colored translucent or transparent material, or it may consist of colored enamel sprayed on the inner wall by well known methods. Some of the light rays which would normally pass through the iight diffusing portion of the cover will be deected bythe screen through the lens 4l and when the color screen is blue, for example, the vertical beam will have a certain daylight quality which improves it for reading purposes.

Of course the rays passing through the light diiusing portion 42 of the cover will also be colored, and the color in the region will be more pronounced because only those rays which correspond in wave -length to the transmission band or bands of the color screen will go through the screen.

It should be noted that the eiiciency of the vertical beam is not impaired in the least by the addition of color since the screen is not placed in the path or the main beam, but only intercepts certain laterally directed rays which other- Cil.

in Figs. 4 6 inclusive, a somewhat similar fixture is shown mounted in the baggage racks extending longitudinally of the car. The cover in this instance may have a smooth rounded outer surface to make it Ysimulate a crystal ball, but" as before, the cover 3l has a lens portion #il and Til wise would pass through the di'using portion l2 or be reflected as white light by the inner surface of that portion.

a light diffusing portion 32. The glass in the diffusing portion 42 may have small bubbles as indicated at il which assist in breaking up the light rays and increasing the general illumination.

Fixture covers of this type have a radiant glow which make them distinctive in appearance and pleasing to the eye.

As best shown in Fig. 5, the xture comprises a box i3 having a hinged cover dB which supports an adjustably positioned bracket 5t which in turn holds thesocket 5l for the lamp 52. The bracket carries at its outer end a reiiector 53 so that no matter where the lamp unit is positioned within the box, the reflector is directly behind the lamp. The bracket is slidably carried on the cover i9 by a pair of screws 5d which are threaded into the vbracket 5B and travel in a slot 55 provided in the box cover.

Since the light xture shown in Figs. 4-6 inf elusive, is closer to the reading plane than the iixture shown in Figs. l-3 inclusive, vertical adjustment of the lamp with respect to the lens il is relatively unimportant although suitable provision may be made at the lower end of the bracket 5@ to accommodate vertical adjustment. As before, a light screen d5 may be used on the inner side wall of the cover 3i for color eect.

The fixtures shown in Figs-7 and 8 are primarily intended for ceiling installations, the one in Fig. 7 comprising a lens cover Et .which is threaded into a somewhat elongated depending base el ln order to give the side or light diifusing portion 5B a better opportunity to provide even ceiling illumination, and the fixture shown in Fig. 8 accomplishes somewhat the same result by having the cover 59 oi substantially spherical form.

'The fixtures shown in Figs. 1 8 inclusive all have the novel aesthetic eiect oi an illuminated crystal and the eiect is more pronounced when at least the side portions of the cover are pro-= vided with bubbles.

In Figs. 9--12 inclusive, two further modidca= tions or the lighting nxture are shown, the covers or which are characterized by having re= entrant lens portions 69 surrounded by a depressed annular diiusing portion tl. In' Fig. 12, the lens is oi the optical type and in Fig. i3, the lens is of the prismatic type. In both forms, however, the lens serves to collect the light rays and concentrate them into a vertical beam to be thrown on the reading plane below.

The marginal diffusing portion di may be provided with beading, as indicated at t2 in Fig. 12 to give the cover an ornate appearance and as sist in the distribution of the light for general y illumination, or it may be plain, as shown in Fig. 13 in which event, the inside annular trough die would be frosted or enameled' to give this portion of the cover light di'using-characterlstics.

In Fig. l2, the x-ture itseli1 com-prises a relector ed having a split neck te forming a jaw which is adapted to adjustably clamp the lamp socket de in its desired vertical position with respect to the lens 58. The socket carries a standard vlamp 5l and ventilation of the nxture is accomplished by convection .with air entering 2,244,737 the reflector through openings B and leaving the reiiector through openings C9.

Attached to the mouth of the rim is a retaining rim 1I provided with screw threads 1I into which the fixture cover is screwed into place and preier ably the upper edge of the cover is serrated as indicated at 12 to cooperate with the locking pawl not shown, which is o! the same character as the pawl I shown in Fig. 2.

-Near the base ot the reiiector 64 is a band or screen 13 which may be color tinted to reflect a certain amount oi color into the main beam transmitted through the lens 60, but a greater amount through the light diffusing portion 6i of the cover.

An alternative method of introducing color into the light emitted by the xture is by employing a color screen 14 (see Fig. 13) of gelatin, or other suitable light illtering material.

The lamp cover shown in Fig. 13 is supported by clips 15 in a retaining ring 16 which is swung from a concealed hinge 11 rigid with the reflector S4. Ventilation openings 6B and 69 are provided as in the fixture shown in Fig. 12.

One advantage of the re-entrant lenses which 'characterize the nxtures shown in Figs. 12 and 13, is that the surrounding diiusing portions 6i tend to screen the light source from the eyes oi persons who are not directly in the vertical beam given out by the nxture. Another advantage is that the total depth of the `fixture is held to a minimum and at the same time, the depressed annular dinusing portion 6I provides better lgeneral illumination immediately adjacent to the beam.

It should be understood that the treatment oi' the lamp cover embodying lens and diffusing a cover portions can be varied to suit conditions, using numerous combinations of frosting, enameling. color tinting and bubbles in the glass, without departing from the spirit of this invention.

Iclaim: A

1. In a lighting nxture, a source of white light, below the source through which light rays are transmitted for producing agiven light distribution, said cover having light transmitting means for throwing a vertical beam of white vuri-'- filtered light and a concentric diiiusing portion for casting light laterally, said difiusing portion including annular prisms adapted to bend the light rays upwardly, and a color screen inside the cover placed with respect to the light source and coverv so as to direct colored light from the source through the light diiiusing portion and to diffuse colored light from the' screen into the vertical beam of white light.

2. In a lighting fixture, a source of white light. a cover below the source through which light rays are transmitted for producing a given light distribution, said cover having light transmitting means for throwing a vertical beam ot white unfiltered light and a concentric diffusing portion for casting light laterally, a reflector behind the source reflecting white light through the light transmitting means, said diffusing portion including annular prisms adapted to bend the light rays upwardly, and a color screen inside the cover placed with respect to the light source and cover so as to direct colored light from the source through the light diffusing portion and to diiuse -colored light from the screen into the vertical beam of white light.

. IEMUEL L. STEWART. 

